A wide assortment of exercise devices have been developed in recent years, spurred on by increasing interest in physical fitness and conditioning. The device of the present invention is an exercise unit which is extremely compact and portable and which is equally suitable for use in organized health or fitness centers as well as in-home use and which will permit a board range of exercises to be performed by an individual safely within a limited area. Previously, as disclosed in my earlier U.S. Pat. No. 4,253,661, I devised an exercise device made up of a thick pad of resilient foam material having a thickness on the order of 6" to 9", and a lower surface or base adapted to rest on a flat supporting surface, such as, a floor. An upper foot-engaging surface is sloped downwardly at a low angle from its maximum thickness, the front and rear sides of the pad being sloped inwardly of the pad toward the upper surface to form an upper foot-engaging surface smaller than the base and a top portion of resilient material smaller than and secured on the upper surface. The separate top portion is comprised of a rectangular member of resilient foam material mounted on a rectangular base of resilient foam material having a center void so that the peripheral portions of the top portion have more resistance to compression leaving a center area of less resistance. As designed, it was possible for the exerciser to perform various jogging and running exercises through the expedient of alternately raising and lowering the feet against the pad or foot-engaging surfaces.
It has been found desirable to devise exercise units of the type disclosed in my earlier patent in such a way as to more effectively control the resistance to compression of the pad by each foot. Generally, when a flat pad surface having sides with angles at 90.degree. undergoes compression, lateral spreading occurs so as to create an inherent instablity, since the limb or limbs will be encouraged to thrust in the direction of least muscular control. In some cases, the lack of predictability of compression of the pad may lead to possible joint or tissue injury. In my prior U.S. Pat. No. 4,253,661, I devised sloped sides in order to reduce the problem of lateral instability. Nevertheless, it was found that the sloped sides as devised did not fully overcome the lateral shearing effect at maximum deflection.
I have now devised a novel and improved exercise unit of the type described which establishes additional control over resistance to deflection and improves the control of compression and rebound rates as well as the containment of developed tension. Moreover, it is desirable to reduce the time element between the compression and rebound phases while at the same time affording proper control over lateral spreading.
Other representative patents in this field are U.S. Pat. No. 2,820,454 to Wright; U.S. Pat. No. 3,434,715 to Brantingham; U.S. Pat. No. 3,627,313 to Schonfield; U.S. Pat. No. 3,634,895 to Childers; U.S. Pat. No. 3,641,601 to Sieg; and U.S. Pat. No. 4,159,826 to Hancock.